Gallon Environment Letter – the daily edition – a policy letter from the Canadian Institute for Business and the Environment

Contaminants in groundwater

A new report from the United States Geological Survey raises concerns about levels of trace elements in water from wells tapping into groundwater. While similar national data do not exist for Canada, the USGS survey suggests that businesses that draw water, especially water for use in food products, from wells may be getting much more than they bargain for.

The USGS findings include:

About 20% of untreated water samples from public, private, and monitoring wells across the nation contain concentrations of at least one trace element, such as arsenic, manganese and uranium, at levels of potential health concern. Public water supplies are monitored and treated for these contaminants but private uses may not be similarly monitored.

Trace elements in groundwater exceed human health benchmarks at a rate that far outpaces most other groundwater contaminants, such as nitrate, pesticides, and volatile organic compounds (VOCs).

Most trace elements, including manganese and arsenic, get into the water through the natural process of rock weathering.

Arsenic, uranium, and manganese, were the trace elements in groundwater that most frequently exceeded USEPA human-health benchmarks.

Differences in the concentration of trace elements are related to the climatic conditions and land use of the area. Drier areas of the United States saw higher concentrations of trace elements in groundwater than humid regions. Meanwhile, wells in agricultural areas more often contained trace elements than those in urban areas. However, wells in urban areas contained concentrations of trace elements that more often exceeded human health benchmarks.

The effects of mixtures of trace elements are poorly understood and could cause further health concerns.